Alkaline detergent



Patented Dec. 1, 1942 2,303,399 ALKALINE DETERGENT Charles schvirart'aT Pittsburgh) l aig a ssignor to Hall Laboratories, 1110., Pittsburgh, Pa.,' acorporation of Pennsylvania 1% Dravving. Application May 1, 1939,

-t msSerial No. 271,178-

i l, 11 c ai s?" (01. 252 135) This invention relates generally to allraline preparati'onsf for example alkaline detergents for cleaning? soft metals and moreparticularly v to i such detergents 'con-taining alkali-metal silicates and" aninhibiting agent I for preventing the alkalinecorrosiohofthemetal. w t in Itis awell' known factthat many highly alkaline detergents? while performing v excellently as cleaners can not b'e usedflfor the; cleaning of soft 1 metals s'uch' as aluminumand tin; since the a'lka 1 lis cor rode and dissolve the' metals quite: readily.

" Many efiorts' have been made ton utilize the excellent detergent properties df highly ialkaline I mixtures and at the same time to prevent; in so far 'as' ""possihle," the attack upon soft Tmetalsz Thus' the use "of certain silicates hasobeeni sum cessful in decreasing to a considerable eXtent the is necessary; hoWei/er, tobe very "careful 'in l the i choicepf silicate used and in the concentration of the 'solution iri order to avoid very serious at tack upo'n the m"'tal 'being washedi :If th'e "con c'entra'tibn o'f -the solution is'too high or too low;

it attacks; the aluminum a'ndthi's places a serious limitation on -th'e type "of "solution which may :be:

employed? Silicats have been but in this case the alkalinity oi the cleaning solution must be adjusted to so low a pH and the temperature of =c1ean=eidropped to such amelitained. --0tlie1 emedies-for the corrosion of tin and alun'i'inuni by-alkalihe cleaners-n have been suggested also. In the case of tin, theius of sodium sulphite has become quite Widespread in recent years. This material decreases theoXygen eonemmmtir ofthe claning solution and sulphit'' is depleted; as itis very shortlyin usualpr'actice; i Where tlie'solution is heated in cont'actwith air, the sodium sulphite is readily converted into sodium" sulpl'iate, which is ineffective inp'reventingcorrosion? 'Brobably'the"mostsuccessful remedy for corrosion *Wh'icflhas been found thus 'far has been lialine"materials in the washing of soft metals. While'in general thesemateriaIs are quite successful in*preventing"corrosion; they have two serious drawbacks? Theytendto coat the metal bing Washd With a greenish yenow: film which in most cases werynndesirabrd M'ostl people used also for cleaning tin sensitive to chromates and the 'operators ascribedmto the formation of non -reacti ve'pro-nusing the cleaners frequently sufierl fromtwhat is known as chromic ulcers, which necessitate cessation of all work withwmaterial containing chromates and which require longvperiods of time for healing.

Itis an object zof the present invention to provide means by which alkaline detergents may be made safe for cleaningvzsoftlmetals. lThe present invention has many advantages over the methods previously employed. Aluminum, tin; zinc, lead,

cadmium orother softmetals thereot maybe treated with solutions of extremelythigh pli at boiling temperatures for long periods of time Without showing any evidence of corrosion. The cleaning solutions preferablyt-have a pH-yof atleast 10 and in'many cases the pl-li istas high as 1201: over. employ 'do not? decrease -in effectivenesse With time, as do the sulphi-tes, buturemain eifective over long wperiods i They zare without harmful effect upon the human skin and will not occasion; the difiiculties: accompanying the use "10f chrom matesondichromates; w I m I have found that "the Water-soluble salts of arsenic and antimony When added improper proportion" to alkali-metal silicates or to; a mixture of alkalies "containing an alkali-n-vmetal silicate as its principal alkaline ingredient rprevent enr tirely the characteristic corroding effectwoftthese silicates. ispreventedlis unknown: but it' probably canbe tective films onthe metal surfaces;

@Sodium metasilicate, sesquisilicate and silicate are strong alkalies,theiraalkalinity increasing in:- the: orderlisted. uIt is=well known that even i the weakest of these, ynamely' sodium metasilicate when used forrexample :towash tin or tin plate: causes rapid: spangling and solution of the tin even at relatively lowvtemperature. .I

have found thatby addinga smalliquantityr of a water-soluble arsenic or antimonylsalt to any of these silicates the corrosive. effect of the solution subsequently made from it .is-reduced; tozero even at boilingwtemperatures ovennlong'periods oftime. 1 i 1 Although I prefer to use the chlorides of arsenic or antimony as the water-soluble salts whichinhibit corrosion of the soft-metals,, I may employ any ordinarily water-soluble ,salt, 1 such as arsenic' iodide, fluoride; or antimony; fluoride or tartrate. Theamount of water-soluble ar-t senic or antimony salts required for preventing corrosion will depend upon L the metal i-to Joe treated the treating solution and theiconditions of treatment. "Under; most conditionatlflprefer The corrosion I inhibitors which I The mechanismwhereby thecorrosion orthoto use at least 5% of arsenic salt based on the weight of the alkali with which it is used. If an antimony salt is employed, it is necessary to use somewhat more than in the case of arsenic. The minimum amount of antimony salt is in the neighborhood of based on the weight of the alkali with which it is used. I have found that abount -20% of antimony chloride (based on the weight of the sodium metasilicate) is required to entirely prevent the corrosion of tin by a 1% solution of sodium metasilicate at boiling temperatures. Under the same conditions, I have found that about 5-10% of arsenic chloride is required to inhibit the corrosion of tin appreciably, although the corrosion is not completely prevented by this material. Under less severe conditions, less of the arsenic or antimony salts may be employed and it will be understood that these salts may be used in amounts above those mentioned without harmful effect, although this is usually unnecessary,

The preferred alkaline material for use in preparing the alkaline detergent solutions are the alkali-metal silicates, such, for example, as

the metasilicates, sesquisilicates and orthosilithe inhibiting salt, it is preferred that the detergent contain an alkali-metal silicate as its principal alkaline ingredient. The inhibiting effect of the antimony is greater in such cases than where the detergent is composed primarily of some other alkali than an alkali-metal silicate.

In the case of arsenic inhibiting salts, although I prefer that they be used With alkalies containing alkali-metal silicate as their principal alkaline ingredient, they inhibit the corrosive effects of phosphates, carbonates, silicates or their combinations with each ther, with or without the addition of sodium hydroxide or other strong alkali.

The water-soluble arsenic or antimony salts act as inhibitors in the presence of mixtures of silicates with sodium hydroxide or other alkalies, soap, casein, defiocculating agents, wetting agents, abrasives and the like.

The alkaline solution containing the corrosion inhibitor is useful in all cases where a highly alkaline detergent is required. It may be used for example in the washing of tin plates, tubes, bakery pans, milk cans, and in tin fabricating plants. In the fabrication of tin plate, or articles made therefrom, it is often necessary to apply grease to aid in the forming operations. This may be removed by the use of a highly alkaline cleaning solution in accordance with the present invention without attack on the tin. The cleaning solutions may be used also in the treatment of aluminum. In this case also, the solution may be used to remove the grease employed in fabricating the aluminum without, however, causing alkaline corrosion of the aluminum.

For washing pans in a bakery where the pans are washed fairly frequently, so that the amount of burned on matter is not excessive, I may use a cleaning composition containing about 95% sodium metasilicate and 5% of arsenic or antimony chloride or other water-soluble salts of these metals. This is dissolved in water to form a solution of a strength between A of 1% and 3%, usually about 1%. The pans might be boiled in the cleaning solution for an hour.

Where the deposits on the bakery pans are excessive, I might use an aqueous solution of a composition containing sodium orthosilicate and 5% of an inhibiting arsenic or antimony salt.

As another example, I might use a, 1% aqueous solution of a composition containing 60% sodium metasilicate, 35% sodium hydroxide and 5% of arsenic or antimony chloride or other watersoluble salt of these metals. I might add to this or to any of the compositions a wetting agent such as a sodium salt of a sulphated fatty alcohol in the amount of 1-3% based on the total weight of the solids. In addition, I might add soap, casein, defiocculating agents, wetting agents, abrasives and the like.

The invention enables the use of highly alkaline solutions containing alkali-metal silicates or other strong alkalies in the cleaning of soft metals without corrosion of the metal. It is preferred that the aqueous solution of the detergent composition have a pH of at least 10 and in many cases it is 12 or over. Thus powerful cleaners may be prepared which by reason of their speed of cleaning, non-corrosiveness and other features referred to are superior to any products now available. Although the invention will probably find its greatest use in connection with preventing the corrosion of aluminum and tin, it is applicable also to the treatment of zinc, lead, cadmium or other soft metals or alloys thereof. The term soft metal as used herein is intended to include any metal or alloy which under the -tion is applicable to inhibiting corrosion by alkaline compositions in general and silicat containing compositions in particular, as for example by the use of such compositions as paints or adhesives. The addition of a water-soluble salt of arsenic or antimony to a silicate containing paint or adhesive will prevent the attack of the paint or adhesive on soft metals, during the time required for the paint or adhesive to set or harden.

The invention is not limited to the examples, which have been given merely for illustrative purposes, or to the preferred proportions, but may be otherwise embodied or practiced within the scope of the following claims.

I claim:

1. An alkaline detergent composition for soft metal, comprising an alkali-metal silicate as its principal alkaline ingredient and being of such character that under normal conditions of use it will corrode the soft metal, and a water-soluble arsenic salt in an amount of at least 5% based on the weight of the alkali-metal silicate to inhibit corrosion of the soft metal.

2. An alkaline detergent composition for soft metal, comprising an alkali-metal silicate as its principal alkaline ingredient and being of such.

character that under normal conditions of use it will corrode the soft metal, and a water-solubleantimony salt in an amount of at least 10% based on the weight of the alkali-metal silicate to inhibit corrosion of the soft metal.

3. An alkaline detergent composition for softmetal, comprising by weight about 95% sodiummetasilicate and about 5% water-soluble saltofv a metal of the group consisting of arsenic and antimony.

4. An alkaline detergent composition for. soft metal, comprising by weight about 95% sodium metasilicate and about 5% of a chloride of metal of the group consisting of arsenic and antimony.

5. An alkaline detergent composition for soft metal, comprising by weight about 95% sodium orthosilicate and about 5% of water-soluble salt of a metal of the group consisting of arsenic and antimony. v

6. An alkaline detergent composition for soft metal, comprising by weight about 95% sodium orthosilicate and about 5% of a chloride of metal of the group consisting of arsenic and antimony.

7. An alkaline detergent composition for soft metal, comprising by weight about 60% sodium:

principal alkaline ingredient and being of such a character that under normal conditions of use it will corrode the soft metal, and an efiective amount of a water-soluble salt of a metal of the group consisting of arsenic and antimony to inhibit the corrosion of the soft metal, an efiective amount being at least 5% in the case of the arsenic salt and at least 10% in the case of the antimony salt, based on the weight of said al- Kali-metal silicate.

10. An alkaline detergent composition for soft metal having apH of at least 10 in aqueous solution and being of such character that under normal conditions of use it will corrode the soft metal, said detergent composition comprising an alkali-metal silicate as its principal alkaline ingredient, and an. effective amount of a water-soluble salt of a metal of the group consisting of arsenic and antimony to inhibit the corrosion of the soft metal, an effective amount being at least 5% in the case of the arsenic salt and at least 10% in the case of the antimony salt, based on the Weight of said alkali-metal silicate.

11. An alkaline detergent composition for soft metal, comprising by Weight about 60 to 95% sodium metasilicate, an eifective amount up to about 35% of an alkali-metal salt having a higher alkalinity than sodium metasilicate, and about 5 to 20%iwater-so1uble salt of a metal of the group consisting of arsenic and antimony.

CHARLES SCHWARTZ. 

